Discharge printing



Patented Nov. 2, 1943 DISCHARGE PRINTING George W. Seymour and George C. Ward, Cumberland, Md., assignors to Celanese Corporation of America, a corporation of Delaware No Drawing. Application February 13, 1940, Serial No. 318,703

6 Claims.

This invention relate to an improvement in the discharge printing of textile materials. More particularly, it relates to the discharge of the color ofthese fabrics so that more desirable white and colored discharge patterns may be obtained.

An object of this invention is to completely remove the discharge products of discharged dyestuffs so as to produce white and illuminated discharge patterns on fabrics of the class described which will permanently retain their original character and original brightness. even after repeated laundering and exposure to sunlight or heat and air. Another object of this invention is to accomplish this result in an economic and expeditious manner.

The discharge printing of textile materials has previously been known to the art and may be accomplished by various modes of procedure. 'In all cases where the fabric is to be discharge printed it is first dyed in the piece to provide the color desired in the background.

when azo dyestuffs are used as the background color, a discharge paste is applied to the fabric in accord with a predetermined pattern and the I prints the complete removal of the discharge azo dye subsequently reduced so that it is split at the azo groups with the formation of various by-products.

In previous processes the by-products have been removed by copious washing with water. While in some cases such washing completely removed them, it was found that in other cases such washing with water only did not remove every trace thereof and as a result the discharge patterns were not permanent in shade,

We have now found that when a fabric that has been dyed with azo dyes and has been locally discharged is washed in a solution of basic reaction the discharge products may be entirely removed and more permanent whites may be obtained. The materials used to impart to the washing solution a basic reaction may be for example, alkali metal compounds such as the hydroxides, carbonates and bicarbonates, quaternary ammonium hydroxides such as trimethyl-benzyl ammonium hydroxide, mono-, di-, and trialkylo'lamines such as mono-,' diand triethanol amine, ammonia, and water soluble aliphatic amines such as methyl amine, ethylamine, isopropyl amine, dimethyl amine, diethyl amine and trimethyl amine. Solutions ranging in concentration from 0.1% up are suitable. The concentrations of basic reacting solutions suitable for this wash are only limited by any deleterious effect high concentrations of basic materials will products gives prints whose characteristics are highly desirable both for brightnes and permanence.

This action of the basic washing solution is very surprising and unexpected. The expected result of such a washing step with a basic reacting solution would be the removal of the solubilized vat from the fabric in the case of illuminated prints. However, upon the actual utilization of the basic washing step this belief is found to be wholly unfounded and very excellent results are achieved.

As a ground color, any suitable azo dyestuff may be used. This invention, however, is particularly of importance in connection with the discharge printing of fabrics which have been dyed with azo dyes, which upon reduction by the discharge agent form products that are reasonably soluble in water.

The discharge paste employed preferably comprises a reducing agent for the azo-dyes which is generally a sulfoxylate formaldehyde, such as sodium or potassium sulfoxylate formaldehyde, and when organic derivative of cellulose fabrics are treated also preferably comprises a swelling agent to permit better penetration of the fabric by the reducing agent, a thickener to keep the paste from undesirable spreading and enough water tomake a thick paste.

The paste may be locally applied to the fabric by any suitable means such as printing with embossed or engraved rollers, by stencilling, or with blocks.

Where the illumination of the discharged portion of the fabric is desired, it is necessary to apply simultaneously with the destruction of the ground color, a dyestufiwhich is either resistant to reduction and is itself a dye for the fabric, or one which can be reversibly oxidized after being vatted to the leuco form. In general it is the vat dyestuffs which are used for illumination since these dyestuffs have the desired quality of being capable of reversible oxidation after being vatted. The vat dyestuffs may be applied to the products remaining on fabric mixed in the discharge paste andthe method of application of the paste is similar to that where white discharges are obtained. However, it is preferable to usean alkali with a vat print in the formulation of the discharge paste. The presence of the alkali solubilizes the leuco vat dye and permits it to penetrate the fabric fully to give even and permanent dyeings.

By proper manipulation it is also possible to obtain a. mixed pattern in which part of the pattern is a white discharge and part is an illuminated discharge.

After the discharge paste is appliedto the fabric by any one of the above-enumerated methods or their equivalent, the fabric is then dried and aged in any suitable ager so ground color will be acted upon by the paste and discharged. For ageing, the continuous ager or the cottage ager may be used. The ageing is generally carried out at about 212 to 215 F. and for a period of time sufficient to discharge the azo dye. This is generally a period of from about to minutes depending on the type of fabric and the particular dyestuffs used.

The discharged fabric may be processed after discharge in either an open soaperor' a rope washer or in any other suitable combination of washing apparatus for the removal of the decomposition products. A vigorous spray of water -may first be utilized to wash out the gum binders and salts followed by the basic wash, or else the fabric may first be given a basic wash and the the fabric removed by thorough washing with water. The sequence of washing operations is not important.

The time during which the fabric is immersed in the basic bath may vary from a few seconds to a half hour and the bath may be kept at a temperature varying from 10 to C. 'It is to be understood that the temperature of the bath and the time of immersion are a function of the concentration of the base and will, of course,

vary as indicated.

In the case where a vat dye is included in the discharge paste composition for illumination of the discharge pattern, the fabric may be washed with water to remove the alkali and precipitate the insoluble leuco vat and the dye may then be oxidized from the leuco form by exposure to air or by an oxidizing bath during the processing. After a final wash with water the fabric is dried.

In carrying out this method of discharge printing, it is best to remove the decomposition products as completely as possible. This is true not onlywhere white discharges are obtained but also where illuminated discharges are desired. The reason for this is fabric from which the decomposition products have not been completely removed to sunlight or to heat and air, or both, will result in their oxidation and the color of the discharge will be affected. If mono amines 0r para-phenylene diamlnes are present, oxidation will yield black compounds similar to Aniline Black"; if meta amines are present Bismarck Brown will be formed. After the formation of these colored products of oxidation it is practically impossible to remove them from white or illuminated discharges and the patterns will not be permanent in shade.

While the exact nature of the amine decomposition products obtained on reduction of the azo-dyestuff is not known with entire certainty,

it is believed,

that the exposure of a that these amines exist as nitrothat the back- 'posed of 12.5%

' dehyde in the discharge agent or as salts of the acid formed by its oxidation. However, regardless of these theoretical considerations by which we do not intend to be limited, these products are substantially completely removed by the alkaline wash.

While this invention is applicable to the treatment of azo-dyed textile fabrics generally it is of particular importance with respect to fabrics or other textile material made of or containing yarns or filaments of any desired organic substitution derivative of cellulose. As examples of such derivatives there may be mentioned cellulose esters for example cellulose acetate, propionate or butyrate, mixed esters such as the acetate-butyrate and acetate-propionate, cellulose ethers, for example ethyl and benzyl cellulose, Y

and the analogous condensattion products obtainable from cellulose and glycols or other polyhydric alcohols. Mixed materials containing one or more of the aforementioned cellulose derivatives together with other textile fibers may likewise be treated in accordance withthe invention. Such materials may'contain, for instance, in addition to a cellulose ester or ether, cotton, Wool, silk or a regenerated cellulose type of artificial silk.

The method of applying the described process is illustrated by the following example:

Example low 3GN," 0.14% Cibacete Yellow GGR and 0.2% of Celliton Brown BRL which topping yields a fabric dyed a deep black. The fabric is then printed in the usual manner with a discharge paste to give a colored and white pattern effect. The paste for the white portion of the discharge pattern is composed of 15.5% of sodium sulfoxylate formaldehyde, 15.5% sodium thiccyanate, 61.4% Supertex gum and water, 1.7% egg albumen, 5.8% titanium dioxide and 0.1% Ultramarine Blue #44. tion of the pattern is printed with a paste comsodium sulfoxylate formaldehyde, 16.6% sodium thiocyanate, 4.2% soda ash, 50.1% "Supertex gum and water and 16.6% of Indanthrene scarlet B.

The printed fabric is then dried and aged at 212 to 215 F. in a continuous ager for a total period of about 15 minutes. By this ageing the azoic ground color is split at the azo groups and reduced to its component amines which may now be washed from the material.

To remove the amine decomposition products the discharged fabric is then processed in an open soaper which consists of a series of troughs and sprays. The fabric is passed through an alkaline reacting bath in the first trough which bath contains a 0.2% solution of sodium hydroxide. After a thorough washing in the alkali bath it is then passed through the remaining troughs and sprays in which it is washed thoroughly by clear, cold water for one hour. The amine decomposition products are now completely removed and the vat dyestuff for the illuminated portion of the print may now be oxidized back from the leuco form by exposure to air or by passing the fabric The illuminated porthrough a bath containing a mild oxidizing agent. The iabric after a final wash in clear, cold water is then dried. The resulting fabric is black upon which is a red and white patterned effect which will permanently retain its original characteristics of brightness and purity oi! color without any fading, staining or darkening due to the formation of oxidation products of the compounds formed in the discharge reaction.

It is to be understood that the foregoing detailed description is merely given by way of illus- V tration and that many variations may be made tion of an alkali metal compound, selected from the group consisting of alkali metal hydroxides and carbonates, to remove the decomposition products of discharged azo dye, said alkali metal compound being present in said solution in a concentration of at least .1% and of at most insuflicient to injure the material.

2. Process for the production of discharge effects on an azo dyed material comprising yarns of cellulose acetate, which comprises locally applying to said dyed material a discharge composition, subjecting the treated material to ageing 50 as to effect a decomposition of said azo dye by said discharge composition, and then washing said material at a temperature of 10 to C. in a non-oxidizing aqueous solution of an alkali metal compound, selected from the group consisting of alkali metal hydroxides and carbonates, to remove the decomposition products of discharged azo dye, said alkali metal compound being present in said solution in a concentration of at least .1% and of at most insuificient to injure the material.

3. Process for the production of discharge effects on an azo dyed material comprising yarns of celluloseacetate, which comprises locally applying to said dyed material a discharge composition, subjecting the treated material to ageing so as to effect decomposition of said azo dye by said discharge composition, and then washing said material at a temperature of 10 to 35 C. in'a non-oxidizing aqueous solution of sodium hydroxide, the concentration of the sodium hydroxide in said solution being .2%.

4. Process for discharge printing of an azo dyed textile material comprising yarns of an organic derivative of cellulose, which comprises printing an azo dyed textile material in a predetermined pattern with a reducing discharge paste containing a vat dyestufi, subjecting .the

printed material to ageing so as to effect a decomposition of said azo dye by said discharge paste; washing said discharged material at a temperature of 10 to 35 C. in a non-oxidizing aqueous solution of an alkali metal compound, selected from the group consisting of alkali metal hydroxides and carbonates, to remove the decomposition products of the discharged azo dye, said alkali metal compound being present in said solution in a concentration of at least .l% and of at most insuflicient to injure the material, washing the material with water and then subjecting the material to oxidation to illuminate the portions printed with the vat dyestuff.

5. Process for discharge printing of an azo dyed textilematerial comprising yarns of cellulose acetate, which comprises printing an azo dyed textile material in a predetermined pattern with a reducing discharge paste containing a vat dyestufi, subjecting the printed material to ageing so as to effect a decomposition of said azo dye by said discharge paste, washing said "discharged material at a temperature of 10 to 35 C. in a non-oxidizing aqueous solution of 'an alkali metal compound, selected from the group consisting of alkali metal hydroxides and carbonates, to remove the decomposition products of the discharged azo dye, said alkali metal compound being present in said solution in a concentration of at least 11% and of at most insufficient to injure the material, washing the material with water and then subjecting the material to oxidation to illuminate the portions printed with the vat dyestufi. l

6. Process for discharge printing of an azo dyed textile material comprising yarns of cellulose acetate, which comprises printing an azo dyed textile material in a predetermined pat,- tern with a reducing discharge paste containing a vat dyestufi, subjecting the. printed material to ageing so as to effect a decomposition of said azo dye by said discharge paste, washing said discharged material at a temperature of 10 to 35 C. in a non-oxidizing aqueous solution of sodium hydroxide in-a concentration of 2% to remove the decomposition products of the discharged azo dye,washing the material with water and then subjecting the material to oxidation to illuminate the portions printed with the vat dyestuff.

GEORGE W. SEYMOUR. GEORGE C. WARD. 

